Oxidative damage can lead to a number of diseases, and can be fatal. The
blm1-1 mutation of
Saccharomyces cerevisiae confers hypersusceptibility to lethal effects of the oxidative, anticancer and antifungal agent, bleomycin. For the current report, additional defects conferred by the mutation in
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Oxidative damage can lead to a number of diseases, and can be fatal. The
blm1-1 mutation of
Saccharomyces cerevisiae confers hypersusceptibility to lethal effects of the oxidative, anticancer and antifungal agent, bleomycin. For the current report, additional defects conferred by the mutation in meiosis and mitosis were investigated. The viability of spores produced during meiosis by homozygous normal
BLM1/BLM1, heterozygous
BLM1/blm1-1, and homozygous mutant
blm1-1/blm1-1 diploid strains was studied and compared. Approximately 88% of the tetrads derived from homozygous
blm1-1/blm1-1 mutant diploid cells only produced one or two viable spores. In contrast, just one tetrad among all
BLM1/BLM1 and
BLM1/blm1-1 tetrads only produced one or two viable spores. Rather, 94% of
BLM1/BLM1 tetrads and 100% of
BLM1/blm1-1 tetrads produced asci with four or three viable spores. Thus, at least one copy of the
BLM1 gene is essential for the production of four viable spores after meiosis. During mitotic growth, mutant
blm1-1 strains grew at reduced rates and produced cells with high frequencies of unusual morphologies compared to wild-type strains. These results indicated
BLM1 is also essential for normal mitotic growth. We also investigated the suppression by the
MSH4 gene, a meiosis-specific MutS homolog, of the bleomycin hypersusceptibility of
blm1-1 mutant cells, and the relationship of
MSH4 to
BLM1. We screened a genomic library, and isolated the
MSH4 gene on the basis of its ability to suppress lethal effects of bleomycin in
blm1-1 cells. However, genetic mapping studies indicated that
BLM1 and
MSH4 are not the same gene. The possibility that chromosomal nondisjunction could be the basis for the inability of
blm1-1/blm1-1 mutant cells to produce four viable spores after meiosis is discussed.
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